I just pulled my OD relay last night and sweated the solder connections where the relay mounts on the board. Lots of stuff in there, not just a simple relay. Mine was working fine 80% of the time but the other 20% I'd push the button and nothing. Then, 30sec to a minute later, if at all, it would jump into OD and the light would come on. Hmm. The driver circuit in the relay was sending an energize signal but the cold solder joints at the relay weren't making adequate contact. When vibration made the connection it went into OD.

You can sit in your car, key on, engine off, with the trans in 4th and push the button. You should hear the OD relay click on and off while pressing the button. If not, you can remove your shift boot and follow the wires from the stick, you'll (at least I did) find a connector. To eliminate the switch, separate the connector and use a piece of wire or paper clip to jump across the contacts. This should toggle the relay on and off. My shift boot was loose anyway so it was easy to pull it off completely. I don't know how it's supposed to attach around the base of the shifter. If your's isn't free, pull out the ashtray and the fuse/relay cover and you should be able to find the OD wires and connector.

Good luck,
--
Erwin in Memphis, '88 745t 183,000 miles, '95 855t For Sale